A great use for Particle Systems is to create smoke and fire effects. Today I'd like to run through a tutorial that explains how to make fire with particles. I'll be using the Softimage Particle System, but the basic principals should apply in any system. We'll make a log in Softimage, create an animated null to control the particle fields and then we will go into the Particle palette and set up the fire.STEP 1--SETTING UP THE SOFTIMAGE SCENE
The first thing we'll need is a log to emit the fire. I went into Softimage and got a primitive cylinder and laid it on its side. Instant log!
Next, we need a null object to float around the top of the fire. This null will be used later in particle to control the motion of the electric and magnetic fields that make the fire flicker.
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Figure 6. -- Click for a larger version.
Click to view the QuickTime movie! Get a null and placed it above the fire. Then go into the Motion module and chose Jitter from the effects menu. Select translate and use values of about .5 for x and z and 0 for y. This will randomly move the null on a flat plane above the fire. You may need to tweak the frequency up to around .2 to make the null's motion a little livelier.
Save the scene.
STEP 2--SETTING UP THE PARTICLE SOURCE
First, load up your Softimage scene. Make a new source using the scene object option and call it log. Choose your previously created cylinder as the scene object. Choose surface generation. This will cause the particles to be emitted from the surface normals of the log. If you preview your scene now, you'll see the particles floating up from the log. Check the regular stream box. This option will cause the particles to be emitted smoothly and uniformly from the log.Here are the other settings in Particle that will enhance the realism of your fire.:
Save.
- Direction: This defaults to emit the particles straight up. Leave it at the default.
- Spread: You want a little bit of spread, so that the particles come off from the sides of the log. I used a value of 20 with a jitter of 10.
- Rate: Crank the rate up to around 200. You'll need a lot of particles to get a good effect.
- Speed: Set the speed to 15 with a jitter of 5.
- Speed Limit: This is what will really control the speed of the particles. Your particles will be in some intense fields, so you need to use the speed limit to keep the particles from flying around like crazy. I used 10 for the minimum and 15 for the maximum.
STEP 3--SETTING UP THE PARTICLES
The main things you need to get realistic fire are lots of particles with high transparency. Use small particles with glow and blur and use local fields to make the fire flicker.Rename your default particle to "fire".
Then set the Particle parameters:
- Friction: this defaults at 0 and should be left there. It is used for wind, an effect we don't use in this system.
- Electric: leave at 0 for now
- Magnetic: leave at 0 for now
- Mass: This defaults at 1 and should be left there. Its used for collisions between unlike particles.
- Life Time: Your fire particles need a pretty short life time. Use values around .5 with a jitter of .5
- Trail life: A little bit of trail life can go a long way. Use a slight value like .2.
- Noise: We won't be needing any noise (random jitter) so leave it at 0
- Sigma: Sigma is used for collisions between like particles and can add to your fire. Use a value of 100 with on jitter.
- Color: Use the default linear particle. Choose an orange color like this one (R 1.00 G .75 B 0). The alpha color must be set very low. I used a value of .01
Save.
- Size: Size does matter! Keep your particles small. Use a value of 1 with a jitter of .1
- Blur: A front blur will stretch-out your particles. Choose front blur with a size of 1.
- Multiply: This is another important setting. It creates instances for your original particles and can really fill-out the fire. Turn multiply with these settings:
- Number: A value of 200 will yield plenty of extra particles.
- Size Factor: Use values of about 100 with a jitter of 100.
- Radius: Enter a value of 1
- Glow: Glow will add that intensity to your fire. Turn it on.
STEP 4--LOCAL FIELDS
Using local magnetic and electric fields will make your fire flicker like a real fire.
Choose local fields from the Cards menu.
Make a new electric field and use the link function to link it to the animated null you made in Softimage. If you previewed at this point, you'll notice that the electric field moves around with the null. Set the strength to 1 and make the drop rate (area of effect) large enough to fully enclose the log (about 15 for me). Go to the particle tab and set the electric tab to 600. When you preview, you'll notice that this causes the fire to converge on the center of the electric field.Click on the Magnetic field tab and make a new magnetic field. Position it in the center of the log. Set the drop rate so that it covers the entire area around the particles. I used a drop rate of 13. Go to the particle tab and set the magnetic value to 80. Now you can go back to the local magnetic field card and play with the strength. You want the particles to swirl as they go up toward the electric field. A setting of 1 or 1.5 should do the trick
That's it! Render it out and enjoy.
Peter Arisman is a digital artist working and living in Seattle. He can be contacted at parisman@lith.com and has a web site at www.3dartists.com.
